Walking with Dragons

How Bearded Dragon Elbows Inform Us of Ancestral Forelimb Posture and Mobility in Dinosaurs and Mammals

The ancestors of mammals and dinosaurs were sprawling quadrupeds. The elbow joint plays an important role in forelimb posture, range of motion, and hand (manus) orientation in tetrapods. Matthew Bonnan’s research focuses on understanding the role of forelimbs—particularly in sauropods, the largest animals to ever walk the earth—in locomotion, posture, and support.

Because lizards retain the ancestral sprawling posture, he and his colleagues used XROMM (X-ray Reconstruction of Moving Morphology) to explore the 3D range of movement and kinematics of the forelimb bones in bearded dragons. Bonnan will discuss the process and results of their research, showing that the lizard elbow is not a simple hinge joint, and that long-axis rotation of both forearm bones relative to the elbow joint is crucial to forward propulsion. Together with previous studies on lizards and other sprawling tetrapods, the results provide evidence that complex elbow movements are an ancient mechanism for efficient overground locomotion.

About the Speaker

Matthew Bonnan is a paleontologist, a professor at Stockton University, and more recently, a singer/songwriter. His childhood obsession with dinosaurs and fascination with animal anatomy grew into a career. Bonnan helped discover three new dinosaur species from South Africa, and his research is dedicated to how functional morphology, how anatomical form follows function, can illuminate locomotion and life histories in dinosaurs, other fossil tetrapods, and even fossil sharks. His current outreach project, Once Upon Deep Time, uses music and art to communicate science.

About the Series

Science on Tap is a monthly speaker series that features brief, informal presentations by Philadelphia-based scientists and other experts followed by lively conversation and a Q&A. The goal is to promote enthusiasm for science in a fun, spirited, and accessible way, while also meeting new people. Come join the conversation!

Featured image: Central Bearded Dragon (Pogona vitticeps) by Max Tibby, CC0, via Wikimedia Commons